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Cutting the invaders and then what? Livestock exclusion after invasive shrub management promotes re-invasion

Vergara-Tabares, David1; Fernández, Lisandro1; Seculin Glur, Julieta1; Carrizo García, Carolina1; Gurvich, Diego1

Published Jun 02, 2026 on Dryad. https://doi.org/10.5061/dryad.cz8w9gjkm

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Abstract

Terrestrial ecosystems degraded by overgrazing and plant invasions challenge restoration programs that must remain compatible with local livelihoods. Invasive shrub control often relies on livestock, which suppress resprouting but generate woody debris that may function as inadvertent herbivore exclusions, with unclear effects on woody plant recruitment. Understanding these effects is critical for guiding restoration.

We conducted a field experiment modifying livestock access using standardized exclosures intentionally assembled from woody debris generated by cutting invasive Pyracantha angustifolia. These debris piles also may provide perching sites for frugivorous birds, offering a unique opportunity to explore assisted natural regeneration pathways following invasive management. By comparing woody plant recruitment inside and outside woody debris patches, we tested their ability to promote native regeneration and potential facilitation of invasives. We selected 28 cuts from 2020 and 28 from 2022, each paired with a control, and measured recruit identity and height in 2024 to evaluate short and medium term dynamics under contrasting grazing pressure.

Woody debris patches reduced livestock browsing and increased woody establishment and growth of invasives, showing rapid growth and higher likelihood of being bird-dispersed, particularly under 4-year exclusions. Community composition shifted among treatments, reflecting species-specific responses and within-site variability.

Synthesis and applications. Woody debris patches prevented observable livestock browsing, facilitating invasive species under prolonged exclusion. Grazing thus operates as a strong biotic filter against invasives, highlighting the need to combine exclusion with targeted management of woody debris. Effective strategies include maintaining livestock access through partial or rotational exclusion, strategically redistributing woody debris to avoid persistent refuges for invasives, and selectively using thorny debris to protect native saplings. Our results offer practical guidance for invasive control and livestock production, contributing to integrated restoration frameworks that consider ecological and socioeconomic dimensions.